Zao's Frost-Covered Trees — The Winter Wonderland Where Ice Monsters Appear

Each winter, on the high slopes of Mt. Zao spanning Miyagi and Yamagata prefectures, nature performs one of its most theatrical transformations. When freezing winds from the Sea of Japan carry moisture-laden air up the mountain and temperatures plunge below -15°C, the fir trees (Abies mariesii) and other conifers on the exposed upper ridges become encased in successive layers of rime ice and wind-driven snow. The resulting formations — fir trees wrapped and reshaped by ice into massive, upright, organic forms — are the famous juhyo (ice trees), known colloquially as "snow monsters" or yukimi dake.

Highlights

The juhyo typically form from late December through mid-February, with the largest and most dramatic formations appearing in January and early February when accumulated ice layers can add enormous bulk to each tree, sometimes making individual firs indistinguishable from one another in a continuous white mass. The ski resort gondola ascends into this landscape, depositing visitors at 1,661 meters where the ice-tree forest stretches across the ridges.

Zao Onsen ski resort, one of the largest in Japan, surrounds the juhyo zone with extensive skiing. Night juhyo tours by snowcat or gondola (when operated) illuminate the ice trees against the dark sky for a particularly theatrical experience. Daytime visitors can ski through the ice-tree forest on designated runs.

Below the mountain, Zao Onsen village offers sulfurous hot spring baths — the outdoor rotenburo is memorable at -10°C — providing perfect post-juhyo warming.

Getting There & Tips

Bus from Yamagata Station to Zao Onsen (about 40 minutes). Gondola tickets purchased at the resort. Juhyo condition reports are available online — check before visiting as formation quality varies by year and by week.

Best Time to Visit

Late January to mid-February for the largest juhyo. February is statistically optimal. The resort's season runs December through late March.

📚 Sources

How the Zao snow monsters form, the growth of the snow monsters as ice and snow cling to the Aomori firs, and viewing by ropeway introduced in this article are organized based on guidance published by the Miyagi Zao and Yamagata Zao tourism associations and operators such as the Zao Ropeway, along with on-site information. Nighttime light-ups and snowcat viewing tours draw on public information from operators. Because ropeway operations, the peak timing and summit weather change with conditions, please confirm official information before you visit.

Visitor Checklist

• Time estimate: About half a day for a round trip by ropeway and a stroll through the snow-monster field. Allow a full day if you add skiing, snowboarding or a viewing tour.
• What to prepare: The summit can drop to nearly minus 20 degrees Celsius, so heavy cold-weather gear and non-slip footwear are essential.
• Best timing: The snow monsters are most developed from late January through all of February. They begin to break down bit by bit in March. Service may be suspended in rough weather.
• Suggested route: Take the ropeway from the base straight up to the snow-monster field. Enjoy the aerial stroll from the gondola, then view the snow monsters up close from the lookouts near the summit station. A winter-limited nighttime light-up tour can also be enjoyed.

Practical Information for Your Visit

• Best season: The snow monsters (juhyo, frost-covered trees) are usually best developed from late January to around February. However, how well they grow varies greatly from year to year with temperature, wind and snowfall, and warm air or strong winds can cause them to collapse mid-season. Check each operator's snow monster reports in advance.
• Season / illumination: On the Yamagata Zao side, the Zao Ropeway holds a snow monster illumination in winter (for the 2025-26 season, December 27, 2025 to February 22, 2026, 17:00-21:00, with the last ascending car leaving Zao Sanroku Station at 19:50). The "Snow Monster Fantasy Corridor Tour" aboard the Night Cruiser requires a reservation and is cancelled if the snow monsters collapse. On the Miyagi Zao side, the snow monster tour by the "Wild Monster" snowcat run by Mountain Field Miyagi Zao Sumikawa operated from December 20, 2025 to March 8, 2026 in the 2025-26 season (check each official website for the dates of the following season).
• Fees: The Zao Ropeway's illumination-period fare for a round trip between Zao Sanroku Station and Jizo Sancho Station is 4,400 yen for adults and 2,200 yen for children, and the Snow Monster Fantasy Corridor Tour costs 7,500 yen for adults and 6,000 yen for children (age 1 to elementary school age). The Sumikawa snowcat tour costs 3,900-5,500 yen for adults and 1,950-2,750 yen for elementary school children and younger depending on the period, and is free for children aged 2 and under (rental of insulated snow boots included). All of these are subject to change, so check the official websites.
• Access: On the Yamagata Zao side, the base is Zao Sanroku Station of the Zao Ropeway in Zao Onsen. On the Miyagi Zao side, the base is Mountain Field Miyagi Zao Sumikawa, and viewing the snow monsters is done on a reservation-only snowcat tour (there is no ropeway for snow monster viewing on the Miyagi Zao side). The Sumikawa snowcat tour requires a reservation, and you must gather at least 30 minutes before departure. The round trip takes about 1 hour 40 minutes to 2 hours.
• Winter closures and road closures: The Zao Echo Line (from the entrance to Sumikawa Snow Park through the Miyagi-Yamagata prefectural border to Zao Bodaira Highland in Yamagata Prefecture) is closed in winter. For 2026 it is scheduled to be open from 11:00 on April 24 until 17:00 on November 4, when the winter closure begins (Zao Town official information); it is due to reopen at 11:00 on April 23, 2027. There are also periods before and after the opening when the road is closed overnight (17:00 to 8:00 the next morning). To travel between the Miyagi and Yamagata sides of Zao in winter, you need a detour such as the expressway rather than crossing the mountains.
• Clothing and gear: Around the summit there are sub-zero strong winds and ground blizzards. You need waterproof and windproof outerwear, thick base layers, a balaclava or neck warmer, gloves, goggles or sunglasses, and insulated boots with non-slip soles (or lightweight crampons). Camera and smartphone batteries drain rapidly in the cold, so bring a spare power source.

* Safety notes (winter): One step outside the summit station and you are in serious winter mountain terrain. Whiteouts in which visibility drops to nothing can occur, and accidents have happened. Be strict about staying on the maintained walking routes and within the markers (ropes and poles), never going alone, and turning back if the weather turns bad. To prevent hypothermia, it is also important not to keep moving in clothes soaked with sweat and to warm up indoors regularly. At the ski areas, going off-piste or into the woods (backcountry) is prohibited because it destroys the snow monster belt and leads to accidents. Beneath the snow lie tree branches and hollows, and if you fall into a tree well it is hard to get out on your own. Ropeways, lifts and snowcats are suspended or cancelled in strong winds or poor visibility. Always check the day's operating status.

* Volcano warnings: Mount Zao is an active volcano and is subject to the volcanic alert level system. On March 6, 2018, the Sendai District Meteorological Observatory lowered the volcanic alert level from 2 (restrictions around the crater) to 1 (be aware that this is an active volcano), and it remains at level 1. Even at level 1, however, eruptions large enough to affect the area around the crater are possible. Volcanic fumes and gas can be seen venting at places such as Maruyamazawa and Furikozawa within the Umanose caldera, and volcanic gas (hydrogen sulfide) is dangerous because it collects in low-lying places and hollows. If you notice anything unusual, leave the caldera immediately. Before you set out, always check the Japan Meteorological Agency's eruption warnings and forecasts as well as volcanic disaster prevention information from Zao Town in Miyagi Prefecture and from Yamagata Prefecture.

* If you are going by car, winter (studless) tires and chains are essential. Watch out for frozen or compacted snow on the road, poor visibility and the state of snow clearing, and avoid pushing your luck behind the wheel.

(Sources: Japan Meteorological Agency "Eruption warnings and forecasts / Mount Zao" / Zao Town, Miyagi Prefecture "Mount Zao volcanic disaster prevention information" / Miyagi Prefecture "Zao Echo Line winter closure and opening information" (Miyagi Prefecture Tourism Promotion Office "Miyagi Marugoto Tanbo") / Zao Ropeway official website "Snow monster illumination" and "Snow Monster Fantasy Corridor Tour" / Mountain Field Miyagi Zao Sumikawa official website "Snow monsters and Okama (snowcat tours)")